Researchers Analyze Oak for Nidaros Cathedral's Centuries-Long Doors
Scientists are meticulously analyzing Danish oak for new doors at Norway's Nidaros Cathedral, focusing on tannin levels to ensure longevity and prevent discoloration from wrought iron fittings.
Nidaros Cathedral, Norway's national sanctuary, is set to receive new doors for its west front portals. These large doors, designed by Danish artist Fredrik Tydén and to be crafted at the Nidaros Cathedral Restoration Workshop (NDR), will be made from English oak (Quercus robur) sourced from Denmark. The doors are intended to last for several hundred years.
A critical aspect of the project involves understanding the oak's composition, particularly its tannic acid content. Tannins in oak can react with the wrought iron fittings planned for the doors, potentially causing black discoloration, or 'rust,' on the wood surface. The goal is to maintain the intended red color of the doors. Factors such as growing location, climate, and the age of the tree influence tannin levels.
Researchers at SINTEF are undertaking the analysis of the oak. Their process involves extracting tannins from the wood using alcohol, creating a solution that is then treated with a dye to quantify the tannin amount. This analysis helps in selecting the best quality oak and determining appropriate surface treatments for the wood, or alternatively, treating the wrought iron to prevent adverse reactions.
The project combines traditional building materials, oak and wrought iron, in a way that is less common today. SINTEF is also testing the tensile and compressive strength of the iron for the hinges. This collaboration between NDR and the Trondheim technology community aims to share new knowledge about historical methods and materials, utilizing advanced analysis to ensure the new doors endure for centuries.
This project highlights the critical role of material science in preserving historical structures. By employing advanced analytical techniques like mass spectrometry to quantify tannin levels in oak, researchers are ensuring the compatibility of traditional materials like oak and wrought iron. This meticulous approach is vital for achieving long-term durability, a key objective in heritage restoration and a growing focus in additive manufacturing for applications demanding extreme longevity.
Edited by the news editor with AI from the original report — please refer to the original source.